1. Field of the Invention
The present invention relates to azo dyes useful in the dyeing of polyolefins and, in particular, to azo dyes having an azo methine linkage and which have utility in the dyeing of metal-modified, or metal-containing, polypropylene textile materials.
2. Description of the Prior Art
Polypropylene, because of its excellent mechanical strength, high elasticity and resistance to solvents, has found increased utility in recent years as filaments, yarns, fabrics, ropes and the like. To provide stability against degradation due to light and to provide reactive sites for dyes, the polypropylene generally contains metal or metal salts or chelates.
Chelatable dyes having specific utility in the dyeing of such metal-containing, or metal-modified, polypropylene are reported extensively in the literature.
Thus, for example, Siegrist et al., U.S. Pat. No. 3,399,027, discloses a process for dyeing polyolefins containing organic nickel chelate complexes with an aqueous dispersion of an azomethine dye. As the azomethine dyes there are disclosed dyes of the formulas: ##STR2## where X is OH or COOH, and
Y is phenylazo or naphthylazo and may be para to X. PA1 B is a salicyclaldehyde or an o-hydroxy-naphthaldehyde nucleus which is unsubstituted or substituted with lower alkyl of 1-4 carbons; lower alkoxyl of 1-4 carbons; halogen or cyano; and PA1 C is a 2-aminopyridine nucleus which is unsubstituted or substituted with lower alkyl of 1-4 carbons; lower alkoxyl of 1-4 carbons; nitro or halogen.
Wolfrum, U.S. Pat. No. 3,630,656, discloses a process for the dyeing and printing of metal-containing propylene with compounds of the general formula ##STR3## where A and B are optionally substituted benzene or naphthalene radicals and R is alkyl. It is disclosed that the substituent --CH=N-- and the --OH group are attached to adjacent carbon atoms and that the substituent --OR and the substituent ##STR4## are also attached to adjacent carbon atoms. A and B cannot simultaneously represent radicals of the benzene series.
Other common chelatable dyes are those containing as the chelating groups, o,o'-dihydroxyazo; o-hydroxy-o'-carboxyazo; o-hydroxy-o'-aminoazo and o-carboxy-o'-aminoazo groups. Although dyes of this type having complexing groups adjacent to the chromophoric portion bind strongly to the metal of metal-modified polypropylene, thus giving it excellent fastness to rubbing, washing and drycleaning, they usually produce dull colors. Additionally there is a drastic change in hue between the chelated and unchelated dye which can cause unevenness on the metallized fiber depending on the concentration of metal in the fiber. This difference in hue can adversely affect the application of these chelatable dyes to the pile of a metal-modified propylene carpet having a non-chelatable backing.